The air force did not directly deny that the F-16 was hit by a Patriot missile.

US experts have joined the Ukrainian investigation into the crash, the air force said.

Meanwhile, five people were killed and 46 injured in Ukrainian attack on the south-western Russian city of Belgorod late on Friday, the local governor said.

Vyacheslav Gladkov also said 37 people, including seven children, were taken to hospital.

Video from a car dashboard, posted on social media and purporting to demonstrate the attack, showed another car being blown up while moving on the road. Seconds later an explosion is seen on the other side of the road.

Ukraine has staged frequent attacks on Belgorod and other Russian border regions in recent months.

Earlier, a Russian attack on the north-eastern city of Kharkiv using powerful plane-launched glide bombs killed six people, including a 14-year-old girl on a playground, and wounded 47 others, regional Governor Oleh Syniehubov said.

The bombs struck five locations across the city, which had a prewar population of 1.4 million people, the governor said.

One of the bombs hit a 12-storey apartment block, setting the building ablaze and trapping at least one person on an upper floor. Emergency crews searching for survivors feared the structure could collapse.

In other developments, Ukrainian rockets hit the Russian city of Belgorod and its surroundings, killing five people and injuring 37, said regional Governor Vyacheslav Gladkov. The region borders northern Ukraine and comes under drone or artillery attacks almost daily.

Zelensky pointed to the Kharkiv strikes as further evidence that Western partners should scrap restrictions on what the Ukrainian military can target with donated weapons.

The Kharkiv strike “wouldn’t have happened if our defence forces had the capability to destroy Russian military aviation at its bases. We need strong decisions from our partners to stop this terror,” Zelensky said.

F-16s are one of the weapons that could be used to hit Russian bases behind the front line.

Oleshchuk said on Telegram that “a detailed analysis” was already being conducted into why the F-16 jet went down on Monday, when Russia launched a major missile and drone barrage at Ukraine.

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“We must carefully understand what happened, what the circumstances are, and whose responsibility it is,” Oleshchuk wrote in the post shortly before his dismissal.

The crash was the first reported loss of an F-16 in Ukraine, where the warplanes arrived at the end of last month. At least six are believed to have been delivered by European countries.

Military analysts say the planes will not be a game-changer in the war, given Russia’s massive air force and sophisticated air-defence systems. But Ukrainian officials welcomed the supersonic jets, which can carry modern weapons used by NATO countries, for offering an opportunity to hit back at Russia’s air superiority.

On the ground, the Russian army is making slow but gradual progress in its drive into eastern Ukraine, while Ukrainian forces are holding ground in the Kursk border region of western Russia after a recent incursion.

The Institute for the Study of War said it expected that Ukraine would lose some Western-provided military equipment in the fighting.

But the Washington-based think tank added that “any loss among Ukraine’s already limited allotment” of F-16s and trained pilots “will have an outsized impact” on the country’s ability to operate F-16s “as part of its combined air defence umbrella or in an air-to-ground support role”.

In other developments, European Union defence ministers agreed in Brussels to boost their training program for Ukrainian troops.

“Today the ministers agreed to raising the target to 75,000, adding 15,000 more by the end of the year,” EU foreign policy chief Josep Borrell told reporters after the meeting.

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“The training has to be shortened and adapted to the Ukrainian training needs,” Borrell said. He added that the EU would set up a small “coordination and liaison cell” in the Ukrainian capital of Kyiv to make the training effort more effective.

So far, 60,000 troops have passed through the bloc’s training scheme, which is conducted outside Ukraine.

AP, Reuters